Degenerative joint disease is commonly attributed to alterations in joint loading and joint kinematics due to traumatic injury. However, the mechanisms by which these alterations cause degenerative joint disease is unclear. Prior to recent advances in the field of computer vision, the ability to study these mechanisms has been limited, due to the lack of a noninvasive method for measuring joint loading and joint kinematics. This research proposal initiates a long-term program to elucidate these mechanisms by studying the in vivo kinematics of the normal and injured wrist. Wrist motion is described simply by two rotations of flexion/extension and radial/ulnar deviation. Early studies described these rotation as occurring about a stationary pivot point for each rotation. Considering the complex anatomy of the carpus, the existence of this relatively simple motion is intriguing, yet remains somewhat controversial. Details of the mechanism by which the individual carpal bones achieve this motion are not complete. The investigators hypothesize that the third metacarpal rotates about a pivot point that is stationary in space, except at the extremes of motion. They further hypothesize that this relatively simple motion is achieved through coupled rotations of individual bones in the proximal carpal row, i.e. they rotate in directions other than that of the wrist. These carpal motions are previously undocumented in vivo and the applicants postulate that they are normally consistent in left and right wrists of men and women. Finally, they hypothesize that ligament injury can alter these carpal motions. To test these hypotheses, they will use advanced feature registration methods. From segmented CT images, 3D surface features of bones will be mathematically defined. These features are invariant to rigid body motion and therefore can be used to calculate kinematic parameters. The first aim is to validate these methods. The second aim is to determine normal 3D in vivo carpal kinematics. The final aim is to determine if and how in vivo 3D carpal kinematics are altered by partial and complete tears of the scapholunate interosseous ligament. It is widely believed that altered kinematics can give rise to many clinical problems. The significance of this work is the accurate measurement of 3D in vivo carpal kinematics in normal wrists and in those with specific ligament injuries. The understanding gained from these studies can benefit diagnosis, surgical treatment, rehabilitation, and the design of prosthetic devices. These findings will form the base of a long-term research program aimed at studying degenerative changes, surgical reconstructions, and rehabilitation in joints. More broadly, the methods developed herein can noninvasively measure 3D motion of any joint using any 3D imaging modality.